Although most prostate cancer deaths are due to metastasis, our understanding of the biological and molecular mechanisms underlying metastatic prostate cancer is still limited. Our proposed research is focused on elucidating molecular mechanisms involved in tumor progression, dissemination, and metastasis of prostate cancer using analyses of in vivo mouse models to inform on human prostate cancer. Thus, we have generated genetically-engineered mouse (GEM) models of metastatic prostate cancer. Using lineage-tracing of these models, we have defined a temporal progression from tumorigenesis to metastasis, and have isolated primary tumor, disseminated, and metastatic cells for molecular analyses. In parallel, we have established state-of-the- art systems biology approaches to accurately integrate molecular data from mouse models to human cancer. By using these advanced systems approaches to interrogate our GEM models, we have identified transcriptional regulatory and epigenetic control mechanisms associated with metastasis progression. In particular, we have shown that a transcription factor pair, namely FOXM1 and CENPF, are master regulators of prostate cancer malignancy. We further demonstrate that the ETS transcription factor, ETV4, is required for metastasis. Moreover, we have found that among regulatory pathways that distinguish metastases from primary tumors are those that are associated with epigenetic modifications, such as the histone methyltransferase, SUV39H1. Thus, we have hypothesized that the molecular cascade associated with metastasis progression includes transcriptional regulatory mechanisms, which drive tumor aggressiveness and promote their metastasis, as well as epigenetic regulators, which are associated with formation of metastases. We will investigate these mechanisms as follows: In Aim 1, we will investigate transcriptional mechanisms associated with metastasis progression, focusing on FOXM1-CENPF and ETV4, to delineate their individual functions and potential cross-talk, as well as to elucidate their mechanism(s) of action. In Aim 2, we will investigate epigenetic regulatory mechanisms that promote metastasis, focusing on histone modifications and particularly the histone-modifying enzyme SUV39H1, to delineate its functions and mechanism(s) of action. In Aim 3, we will pursue discovery-based systems analyses to investigate key molecular aspects of metastasis progression, in particular, to identify mechanisms associated with organ specificity of metastases and molecular mechanisms associated with clonal relationship of tumors and metastases.